| Objective To investigate the role of microRNA (miRNA) let-7 and its regulation on high mobility group A2 (HMGA2) protein expression in esophageal squamous cell carcinoma (ESCC). Methods Chemical synthesis of let-7 or its inhibitor were transfected into a human ESCC cell line Eca109. The expression of let-7 and HMGA2 mRNA in the transfected cells were detected by qRT-PCR method, and the protein expression of HMGA2 were examined by western blot technique. Specimens of ESCC and normal tissues were collected from ESCC patients, the expression of let-7 and HMGA2 mRNA were detected by qRT-PCR method, and the protein expression of HMGA2 was examined by immunohistochemistry (IHC). Results In the Eca109 cells transfected with let-7, the increased accumulation of let-7 repressed cells proliferation, and resulted in decrease of HMGA2 protein levels with approximately 30%. However, in cells transfected with let-7 inhibitor, the decreased accumulation of let-7 promoted cells proliferation, and resulted in increase of HMGA2 protein levels with approximately 64%. Both of them had no effect on levels of HMGA2 mRNA. Compared with corresponding normal samples, the expression of let-7 was significantly lower in the tumor samples(P<0.05), and significantly correlated with lymph node metastasis of ESCC(P<0.05). The protein expression of HMGA2 was significantly higher in the tumor samples compared with corresponding normal samples(P<0.05), however, the expression of HMGA2 mRNA had no obvious significance between them. Conclusion 1. Let-7 and HMGA2 were involved in ESCC carcinogenesis.2. Let-7 could repress cell proliferation of ESCC.3. Let-7 was lowerexpressed in ESCC, and there was a correlation between let-7 lower expression and lymph node metastasis in patients of ESCC. As well as, HMGA2 protein expression was significantly higher in ESCC than that in corresponding normal tissues.HMGA2 may negetively regulated by let-7 at the post-transcriptional level in ESCC.
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